Import shared props in Roslyn5000 project

Replace inline project properties in the Roslyn5000 csproj with imports of the shared props and projitems to centralize configuration. Also add a new conditional DefineConstants in CommunityToolkit.Mvvm.CodeFixers.props to define ROSLYN_5_0_0_OR_GREATER when MvvmToolkitSourceGeneratorRoslynVersion >= 5.0.0, enabling feature flags for Roslyn 5.0.

Author: Sergio0694

src/CommunityToolkit.Mvvm.CodeFixers.Roslyn5000/CommunityToolkit.Mvvm.CodeFixers.Roslyn5000.csproj

@@ -1,9 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
-  <PropertyGroup>
-    <TargetFramework>net10.0</TargetFramework>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
-  </PropertyGroup>
+  <Import Project="..\CommunityToolkit.Mvvm.CodeFixers\CommunityToolkit.Mvvm.CodeFixers.props" />
+  <Import Project="..\CommunityToolkit.Mvvm.CodeFixers\CommunityToolkit.Mvvm.CodeFixers.projitems" Label="Shared" />
 
 </Project>

src/CommunityToolkit.Mvvm.CodeFixers/CommunityToolkit.Mvvm.CodeFixers.props

@@ -24,6 +24,7 @@
     <!-- Also define "ROSLYN_<MAJOR>_<MINOR>_OR_GREATER" build constants, so the generator code can multi-target whenever needed and add any required polyfills -->
     <DefineConstants Condition="$([MSBuild]::VersionGreaterThanOrEquals($(MvvmToolkitSourceGeneratorRoslynVersion), 4.3.1))">$(DefineConstants);ROSLYN_4_3_1_OR_GREATER</DefineConstants>
     <DefineConstants Condition="$([MSBuild]::VersionGreaterThanOrEquals($(MvvmToolkitSourceGeneratorRoslynVersion), 4.12.0))">$(DefineConstants);ROSLYN_4_12_0_OR_GREATER</DefineConstants>
+    <DefineConstants Condition="$([MSBuild]::VersionGreaterThanOrEquals($(MvvmToolkitSourceGeneratorRoslynVersion), 5.0.0))">$(DefineConstants);ROSLYN_5_0_0_OR_GREATER</DefineConstants>
   </PropertyGroup>
 
   <ItemGroup>